.300 BLK build.

Slimjim · Oct 3, 2012

So i'm building a PSA lower i bought during their black friday sale into a .300 BLK carbine. This will be for Supersonic use only. Dont plan on getting a can for it, Although if i do buy a suppressor it'll be for .308 and for my REPR foremost, With my A4 clone using it next.

Anyway. I picked up one of the AR-Stoner 16" 1:8 stainless barrel .300 blk carbine gas system.

PSA lower.
PSA std buffer, spring.
PSA milspec buffer tube.
PSA LPK.

I'm getting to the point where i have to choose the rest of my components. I'm considering:

YHM low profile gas block. (I cant find much of a difference between the YHM, the troy, and the other gas blocks that share this same shape)
I have to find an upper receiver thats in stock, may just pick up a PSA blem.

Rainier arms 12" modular handguard.
Rainier arms .300 blk flash hider.
HK 416 Grip.
Aimpoint ML2
Magpul STR stock.
PSA Bolt and carrier.
BCM gunfighter charging handle
Ambi safety.

I may be missing some parts here, It will have some type of flip up sights.

I like the .300 Blk cartridge in that it gives a bit more power to the AR platform, with a bigger heavier bullet.

HT4 · Oct 3, 2012

You might want to consider a heavier buffer.

Slimjim · Oct 3, 2012

HT4 said:
You might want to consider a heavier buffer.

I'll consider an H buffer depending on how the gun runs. I may buy an H buffer as well.

BradMacc82 · Oct 3, 2012

PSA blem's work fine, I used one for my 300BLK build, T-marks weren't filled - aside from that it was perfect.

Why are you going with a carbine length system? Just curious.

Slimjim · Oct 3, 2012

BradMacc82 said:
PSA blem's work fine, I used one for my 300BLK build, T-marks weren't filled - aside from that it was perfect.

Why are you going with a carbine length system? Just curious.

Only shooting supersonic rounds. Also thats what the midway barrels are available with.

BradMacc82 · Oct 3, 2012

Ahh ok.

I tossed around a few options on barrels myself when in process, wound up going Noveske 16" (pistol length gas) - if you can swing it, it's definitely worth it.

Aside from a load development issue, it's been a dream and runs like clockwork.

Slimjim · Oct 4, 2012

Can anyone tell me a difference in the YHM low profile gas block and the troy besides the logo?

clandestine · Oct 4, 2012

Vltor Gas Block is pinnable like they are supposed to be.

Slimjim · Oct 4, 2012

Chad, I was hoping you would respond. This barrel is already dimpled for a gas block. And i have seen a test where it took quite a bit of force to dislodge a properly dimpled and lock-tited gas block. But you believe they should still be pinned, I'm asking, not arguing.

clandestine · Oct 4, 2012

Slimjim said:
Chad, I was hoping you would respond. This barrel is already dimpled for a gas block. And i have seen a test where it took quite a bit of force to dislodge a properly dimpled and lock-tited gas block. But you believe they should still be pinned, I'm asking, not arguing.

For a Banch Gun thats fine. But for something you may do mag dumps or use seriously, it will generate enough heat in the Gas Block Area to cause any Loctite to break down or cut loose. Once that happens the Clamping or Set Screws are only relying one the initial torque from a "cold" installation set. Once the larger parts like the Gas Block heat up it can cause torqued things to loosen. If you do use a set screw method dimpling is a good thing to do, I also recomend staking the Set Screws so they cant back out.

I havent seen the test, but I have seen more AR's than I can count used for Carbine Classes, Bump Fire Stocks, and Patrol Carbines that became single shots because heat or ause dislodged a clamp on oe set screwed FSB/Gas Block.

Aluminum Gas Blocks are the worst because they erode with any serious use and tend to allow Gassing Changes depending on where the Erosion takes place.

I cross pin everything I can except clamp on Gas Blocks when possible. Its up to you to determine wether its needed for your applications/use.

Slimjim · Oct 4, 2012

http://www.militarymorons.com/weapons/ar.optics2.html

Theres the test, of course that was a clamp style, and not a set screw style. What does it cost to have the pin drilled in an AR barrel usually?

Also, with the carbine length gas system, running super sonics only. What are your thoughts on the buffer setup, Will the STD be fine, or should i also consider an H buffer?

BradMacc82 · Oct 4, 2012

Slimjim said:
Also, with the carbine length gas system, running super sonics only. What are your thoughts on the buffer setup, Will the STD be fine, or should i also consider an H buffer?

Start with the heaviest buffer, and keep going progressively lighter till it locks back on an empty mag.

It's what we did when he helped out on my build.

clandestine · Oct 4, 2012

Slimjim said:
http://www.militarymorons.com/weapons/ar.optics2.html

Theres the test, of course that was a clamp style, and not a set screw style. What does it cost to have the pin drilled in an AR barrel usually?

Also, with the carbine length gas system, running super sonics only. What are your thoughts on the buffer setup, Will the STD be fine, or should i also consider an H buffer?

Thanks, Ill take a look at that.

Depending on the gas block it can run fron $40-$95 if I did it. The price varies on the Hardness of the Barrel (Some Require Carbide Bits), wether I have to mill a flat on the Gas Block (Its sometimes needed on certain Gas Blocks to get the hole to drill/track straight). If you try to drill a hole on an angled surface the bit wants to deflect and not drill straight. If you mill a flat it will drill perfectly.

I think Adco does it cheaper than I though.

What I do offer is what Brad sugested below. I have every buffer to find the best weight/spring combo for your AR. You have to provide the ammo. I charge $40 for this testing for an unsuppressed application with provided ammo.

BradMacc82 said:
Start with the heaviest buffer, and keep going progressively lighter till it locks back on an empty mag.

It's what we did when he helped out on my build.

I agree. Theres no one answer because no 2 setups will be perfectly identical because of the differing variables with build components.

Mdeng · Oct 5, 2012

Trust me you want a pinned gas block. After going back and forth with AAC, they sent me a RMA shipping lable. My AAC 9" upper only worked for 40 slow fire shots before the gas block started to move. I hope to have it back by Christmas.

BradMacc82 · Oct 5, 2012

Mdeng said:
I hope to have it back by Christmas.

Damn..., that sucks big ones.

If nothing else, at least it's getting taken care of.

clandestine · Oct 5, 2012

Mdeng said:
Trust me you want a pinned gas block. After going back and forth with AAC, they sent me a RMA shipping lable. My AAC 9" upper only worked for 40 slow fire shots before the gas block started to move. I hope to have it back by Christmas.

So the retest with the Rifle Spring AAC Suggested didnt go as planed I take it?

.300 BLK build.

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